Justification:
This species is endemic to the northern part of the Isle of Arran in western Scotland. It qualifies as Critically Endangered (EN B1ab(iii)) due to its highly restricted extent of occurrence and area of occupancy (4 km2), found in a single location. There is a continuing decline in habitat quality and extent. The main threats to the species are decline in habitat quality and grazing. In addition, it has a low population size of 436 individuals, however 80% of these are not thought to be reproducing regularly, so the number of mature individuals are estimated at 200.

The species is restricted to the Glen Catacol and Glen Diomhan in the north of the Isle of Arran in Scotland. Trees have occasionally been planted elsewhere on Arran (Rich et al. 2010). Both the estimated extent of occurrence (EOO) and the area of occupancy (AOO) are estimated at 16 km2, however the actual occupancy is very much more restricted (<4 km2) and the actual EOO is 4 km2.

From a systematic survey in 1997, 436 trees remained in seven sites (Robertson 2004). Smaller and stunted trees of less than 1.5 m (about 50% of population) have no flowers or fruit and are not reproducing. The population size of the species may therefore be around 200 mature individuals. Most trees (275) are found in a single site, with the other sites having about 20-40 trees. Some populations have been lost to fires or landslides, however there have been some signs of increased population size at some sites. Therefore the population trend is not clear (Rich et al. 2010).

This shrub or small tree occurs on steep-sided gorges, in scrub on steep granite crags and in remnant woodland on a stream bank. The soil is strongly acid and peaty. It often co-occurs with Sorbus arranensis (Rich et al. 2010).

The main threat is decline in habitat quality, decline in the surrounding woodland has exposed the species to harsh weather conditions and grazing pressure (Robertson 2004). Trees are lost to wind-throw and snow-break as well as rock falls. Trees are also threatened by grazing from hare and deer. In addition, pollen viability and seed set is low. Landslides and fires may also be a threat to the species. There is also significant seed predation from Apple Moth maggots.

Much of the population is in Glen Diomhan (previously designated as a National Nature Reserve). The erection of a deer fence around Glen Diomhan has been partially effective in excluding herbivores. Planting of trees has also been carried out with limited success. Conservation efforts aim to increase the surrounding woodland to provide shelter as well as improving soil quality and reducing soil erosion (Robertson 2004). It is listed as a UK BAP priority vascular plant species (JNCC 2010). Conservation work is on-going by Royal Botanic Gardens Edinburgh and Scottish Natural Heritage. Sorbus pseudofennica is listed as Vulnerable in the Red List of Great Britain (Cheffings and Farrell 2005) and in Oldfield et al. (1998). There are several records of Sorbus pseudofennica in ex situ collections in botanic gardens (BGCI 2015) and is recorded as present in an ex situ seed bank collection (ENSCO 2015).